1. Field of the Invention
This invention relates to complexes of PVP-H.sub.2 O.sub.2, and, more particularly, to a complex of a strongly swellable, moderately crosslinked PVP and H.sub.2 O.sub.2 which is substantially stable in aqueous medium towards decomposition of H.sub.2 O.sub.2 therein.
2. Description of the Prior Art
Stabilized H.sub.2 O.sub.2 compositions have found wide utility in commercial and industrial applications, e.g. as antiseptics, disinfectants, sterilization agents, bleaching materials, washing concentrates, etchants, in cosmetic preparations, as cigarette filters, and as a catalyst in polymerizations requiring a free radical source. In biological applications which require an antiseptic, disinfectant or sterilization agent, such H.sub.2 O.sub.2 compositions require release of an effective amount of oxygen at a desired rate.
The prior art has provided such complexes in various forms. For example Shiraeff, in U.S. Pat. Nos. 3,376,110 and 3,480,557, disclosed that a stabilized hydrogen peroxide composition of hydrogen peroxide and PVP could be prepared by mixing an aqueous solution of PVP and a substantial excess of H.sub.2 O.sub.2, and evaporating the solution to dryness at 90.degree.-100.degree. C. The H.sub.2 O.sub.2 content of the composition obtained, however, was quite variable, ranging from 2% to 70% by weight, and considerable water was present in the final composition. Prolonged drying of the composition, in an attempt to reduce its water content, resulted in a further loss of H.sub.2 O.sub.2. The resultant product was described as a brittle-film, or a transparent, gummy, amorphous material, which lost a considerable portion of its H.sub.2 O.sub.2 content upon standing, or in aqueous solution.
Merianos, in U.S. Pat. No. 5,008,093, provided free-flowing, stable, high purity, substantially anhydrous complexes of linear (water-soluble) and crosslinked (water-insoluble) PVP and H.sub.2 O.sub.2 in defined molar ratios of 1:1 or 2:1. These free-flowing products were made by reacting a suspension of PVP and a solution of H.sub.2 O.sub.2 in an anhydrous organic solvent, such as ethyl acetate. The free-flowing PVP-H.sub.2 O.sub.2 powders made by Merianos represented a significant advance in this art because its peroxide content was reproducible and the complex in this form could be processed easily into pharmaceutical formulations. However, the process could not be scaled up easily for commercial manufacture of the product.
Biss, in U.S. Pat. No. 5,077,047, described a commercial process for the production of such linear (water-soluble) and crosslinked (water-insoluble) PVP-H.sub.2 O.sub.2 complexes in the form of free-flowing powders. In the Biss process, a fluidized bed of the PVP powder was maintained at a reaction temperature of from ambient to 60.degree. C. Then the PVP bed was contacted with finely-divided droplets of an aqueous H.sub.2 O.sub.2 solution containing about 30 to 85% by weight hydrogen peroxide. The resultant product was a stable, substantially anhydrous, free-flowing powder of such PVP-H.sub.2 O.sub.2 complexes having a 1:1 molar ratio of its components.
Shih, in U.S. Pat. No. 5,073,614, described the preparation of strongly swellable, moderately crosslinked PVP having a predetermined aqueous swelling parameter and a defined viscosity which had effective thickener and gelling properties.
Accordingly, it is an object of the present invention to provide an aqueous stable PVP-H.sub.2 O.sub.2 product which has gelling and thickening properties in solution.
Another object of this invention is to provide an aqueous stable complex of PVP-H.sub.2 O.sub.2 having a 1:1 molar ratio of components, the PVP being strongly swellable and moderately crosslinked, as defined by characteristic aqueous swelling and viscosity parameters. These and other objects and features of the invention will be made apparent from the following more particular description thereof.